<!-- 用来显示父子组件的嵌套 -->
<div class="index-container">
    <div class="index-left">
        <ul>
          <li><a [routerLink]="[ '/index/sport' ]" >体育</a></li>
          <li><a [routerLink]="[ '/index/music' ]" >音乐</a></li>
        </ul>
    </div>
    <div >
          <router-outlet></router-outlet>
    </div>
</div>
